Enter year, month, day, click "Compute J.D." and you will get
julian day, week day and a time table of next Moons and Eclypses.
For reverse operation enter julian day, then click "Compute Date".

Enter number n of days and click Sum to get date n days after;
enter a second date an click Difference to get the number of days between the two dates.
.

Astronomical events

Notes

New Moon: First quarter: Full Moon: Last quarter:

(Times are in U.T. i.e. Greenwich Mean Time;
Moon phases are approximated with a maximum error of about 2 min;
for Sun eclypses the visibility zone is largely approximate
if you want the eclypses of a given year, you can enter January 1, then May 1 and finally Sep 1,
to get a complete list for the year).

This perpetual calendar calculates Julian Day,
day of the week, next lunar phases and eclipses, given day, month, year;
the passage from Julian calendar to
Gregorian is fixed to Oct 4-15 1582.
You can also enter Julian Day and calculate date.

For years preceding -45 (4BC), which was Julian Calendar beginning year,
dates are computed according to a
backdated Julian calendar, not Numan Calendar (information about the latter
is really too limited).

For years between -45 (4BC) and 8AD I tried to take into account
changes of month names and lengths
and the error made by roman clergy in the compute of
leap years (every three instead of four).